Treatment of rubber



Patented Mar. 17, 1942 TREATMENT OF RUBBER Clyde Coleman, Montclair, N.J., assignor to United States Rubber Company, New York, N. Y., acorporation of New Jersey No Drawing. Application March 28, 1939, SerialNo. 264,595

6 Claims. (Cl. 260800) This invention relates to the treatment of rubherand similar oxidizable materials, and more particularly to a new classof age resistors.

An object of the invention is to provide a new class of anti-oxidants orage resistors for organic substances which tend to deteriorate byabsorption of oxygen from the air, for example, goods of rubber orallied gums, unsaturated fatty oils such as unsaturated vegetable oils,essential oils, petroleum oils and their derivatives such as gasolines,soaps, aldehydes, synthetic resins, turpentine, paints and varnishescontaining drying oils, and the like. A further object of the inventionis to provide chemicals which additionally act as flex-improvers oranti-flex cracking agents for vulcanized rubber such as tire treads,which undergo repeated strains during use. Further objects will beapparent from the following description.

According to the invention rubber and the like as aforesaid is treatedwith a compound having the general formula A-X where X is the ringnitrogen atom of a 2,5-dia1kyl pyrrol group, and A is an aliphatic groupcontaining at least one carbon atom and preferably two or moreopen-chain carbon atoms. The aliphatic group A may have as a substituenta hydroxyl group, and the chemicals accordingly include N-alkyl2,5-dialkyl pyrrols and N-alkylol 2,5-dialkyl pyrrols.

The aliphatic radical A may be a branchedchain radical, or a straightchain radical, and the hydroxyl group may be situated at any point onthe chain. Accordingly A may be, for example, methyl, ethyl, propyl,isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, amyl, etc., or acorresponding alkylol radical.

The following are illustrative of the chemicals included in theinvention:

1. Nn-butyl-2,5-dimethyl-pyrrol CH3-CH2 CH2'CH2 N r H CH: II.N-beta-propylol-Z,5-dimethyl-pyrrol =CH 0 Ha-CHC Hr-N l OH (I): H

As further examples, when A is any of the above aliphatic groups, X maybe:

(1) 2,5-dimethyl pyrrolonyl (2) 2,5-dimethyl pyrrolidinyl Thesecompounds may be made in several ways, as for instance, by treating analkyl halide, or in case the aliphatic radical is to contain a hydroxylgroup, an alkyl halo-hydrin, with the proper heterocyclic secondaryamine, in the presence of an inorganic base. According to another typeof reaction, N-ethylo1-2,5-dimethyl pyrrol is made by condensingethanol-amine with acetonyl-acetone.

In the table below are given data showing the effectiveness of certainof these chemicals in preventing the cracking of bent rubbervulcanizates exposed to the sun.

A tread stock containing smoked sheet, carbon black, softeners,antioxidant, sulfur, zinc oxide and accelerator was prepared and dividedinto three portions, To one part was added an amount ofN-n-propyl-2,5-dimethyl-pyrrol equal to 1% on the rubber, and to anotherportion a like amount of beta-propylol-2,5-dimethyl-pyrrol. The sameamounts of the same chemicals were also added to portions of a gum stockcontaining only rubber, sulfur, zinc oxide, stearic acid andaccelerator. After vulcanization the stocks were tested for resistanceto cracking by cutting pieces of convenient size and bending them intoloops which were fastened to a board. They were then exposed to the sunin Florida. The results are shown below. The symbols in the table havethe following meanings:

7 days ex- 34 days ex- 67 days exposure posure posure Tread Gum TreadGum Tread Gum N-beta-propylol-2, 5-

t y p 0 0 N-n-propyl (25 d1- t y pr D- 0 0 sheet and thread rubber,rubberized fabrics,

molded goods, boots and shoes, etc., Whether vulcanized in a mold, inopen steam, in hot air, or in the cold by the so-called acid process.The proportion of the anti-oxidant may vary from about 0.1% to althougheither smaller or greater proportions may be found useful. If thematerial to which it is added is a liquid such as rubber cement or anoil, the antioxidant may be dissolved therein in a suitable smallproportion. The antioxidant may be incorporated.

into solid substances by milling or mastication,

and prepared for incorporationinto dispersions or solutions either inpowder, paste or solution form, or applied in such formsforincorporation by diffusion, to the surfaces of vulcanized orunvulcani'zed rubber goods.

Having thus described my invention, What I claim and desire to protectby Letters Patent is:

1. A-process of" inhibiting the deterioration of organic substancesWhich tend to deteriorate by absorption of oxygen from the air whichcomprises treating the same with a compound having the general formulaAX where X is the ring nitrogen atom of a 2,5-dialkyl pyrrol group, andA is an aliphatic group containing a plurality of open-chain carbonatoms, with one carbon atom directly attached to said ring nitrogenatom.

2. A process of inhibiting the deterioration of.

organic substances which tend to deteriorate by absorption" of oxygenfrom the air which comprises treating the same with an N-n-propyl-(2,5-dialkyl pyrrol) 5. An organic substance which tends to deteriorateby absorption of oxygen from the air contraining a compound having the;general formula AXv where X is theirin'gsnitrogen atom of a 2,5-dia1kylpyrrol group and A is an aliphatic group containin aplurality ofopen-chain carbon-atoms, one carbon atom of which is directly attachedto said ring nitrogen atom.

6. A rubber product containing an anti-oxidant having thegeneral-formula A--X where X is the ring nitrogen atom of a 2,5-dialkylpyrrol group, and A is an aliphatic group containing a plurality ofopen-chaincarbon atoms, a carbon atom of which is directly attached tosaid ring nitrogen atom. 1

CLYDE COLEMAN.

